A comprehensive review of state-of-the-art optical fiber and preform index-profiling methods has been prepared. The advantages and disadvantages of the various approaches are discussed. Important parameters include measurement accuracy, resolution, simplicity, and the nondestructive features of some methods. Both optical and nonoptical techniques have been treated. Resolution considerations probably favor the refracted near-field technique and this may be a decisive factor for the measurement of single-mode fibers. Simplicity of apparatus lies with near-field methods generally so that the bound near-field method is most often used for dimensional measurements. Preform profiling is dominated by deflection function methods, usually accompanied by spatial filtering or focusing. Methods restricted to certain classes of fiber, such as the far-field approaches, are less attractive and, consequently, do not receive as much use.

Optical fiber and preform profiling technology

A comprehensive review of state-of-tie-art optical fiber and preform index-profiling methods has been prepared. The advantages and disadvantages of the various approaches are discussed. Important parameters include measurement accuracy, resolution, simplicity, and the nondestructive features of some methods. Both optical and non-optical techniques have been treated. Resolution considerations probably favor the refracted near-field technique and this may be a decisive factor for the measurement of single-mode fibers. Simplicity of apparatus lies with near-field methods generally so that the bound near-field method is most often used for dimensioned measurements. Preform profiling is dominated by deflection function methods, usually accompanied by spatial filtering or focusing. Methods restricted to certain classes of fiber, such as the far-field approaches, are less attractive and, consequently, do not receive as much use.

Optical Fiber and Preform Profiling Technology

The influence of convex striations of vapor phase axial deposition (VAD) optical fibers on transmission characteristics has been analyzed. These convex striations are inherent in optical fibers made by VAD and cause refractive-index fluctuations in both radial and axial directions. The phase of the sinusoidal fluctuations in the radial direction varies periodically along the fiber axis. Numerical analysis shows that bandwidth degradation due to sinusoidal fluctuations in the radial direction can be alleviated by a periodic phase variation in the axial direction.

Transmission characteristics of VAD multimode optical fibers

This is the second volume of a series intended to describe optical fiber measurement systems developed at the National Bureau of Standards. The topics covered in this volume are attenuation, bandwidth (frequency domain), and far-field near-field radiation patterns. Each chapter includes a tutorial section and a detailed description of the apparatus. The volume concludes with a glossary of optical communications terms.

Optical Fiber Characterization Attenuation Frequency Domain Bandwidth and Radiation Patterns | NIST

Intermodal dispersion compensation in spliced graded-index optical fiber is investigated. Group delay times of modes in individual and spliced fibers are exactly analyzed using the Wentzel-Kramers-Brillouin (WKB) method. It is found that in actual fibers whose refractive index profiles are not represented by the power-law function, the compensation effect is less remarkable than that predicted from the power-law approximation. The baseband bandwidth of spliced fiber, composed of under- and over-compensated index profile fibers, is calculated based on the measured index profile. As a result, the measured bandwidth is found to be well predicted with an error less than 5 percent.

Exact analysis of intermodal dispersion compensation in spliced graded-index optical fibers

A modified bounded-mode near-field scanning method for determining the refractive-index profiles of optical fibres is described. The technique is simple to implement and allows the fibre numerical aperture and geometry to be measured.

Fibre refractive-index profiling by modified near-field scanning

A method for calculating the modal delay characteristics of multimode optical fibres with arbitrary refractive index profiles is described, which is quick, accurate, and can be used with either an analytical or an experimentally measured profile.

Method of calculating the modal delay for optical fibres with arbitrary refractive-index profiles

A new method for measuring the refractive-index profiles of single-mode fibres is described. The technique is simple to implement, has good resolution and allows fibre numerical aperture and geometry to be measured.

Near-field scanning technique for profiling single-mode fibres

The light acceptance properties of fibre samples prepared for the modified near field scan technique are derived. The effect of limiting the imaging lens NA and of varying the sheath refractive index will also be discussed.

D.H. Irving

Papers

Fibre refractive-index profiling by modified near-field scanning

Method of calculating the modal delay for optical fibres with arbitrary refractive-index profiles

Near-field scanning technique for profiling single-mode fibres

Fibre light acceptance for modified near field technique

Modified near-field intensity scanning of step-index fibres